<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .father {
            background-color: yellowgreen;
            width: 400px;
            height: 400px;
            position: relative;
        }
        
        .son {
            background-color: aqua;
            width: 100px;
            height: 100px;
            /* position: absolute; */
            /* position: fixed; */
            right: 50px;
            bottom: 100px;
        }
    </style>
</head>

<body>
    <div class="father">
        <div class="son"></div>
    </div>

</body>

</html>